Leptospirosis in Swine

Leptospiral serovars pomona and bratislava are the most common causes of porcine leptospirosis in the USA, with serovars grippotyphosa, icterohaemorrhagiae, and canicola occasionally implicated. Swine are maintenance hosts for serovar bratislava, and infected pigs rarely develop signs typical of acute leptospirosis—rather, reproductive failure as evidenced by infertility and sporadic abortion are the most common clinical signs, and venereal transmission may occur. Serovar pomona, in contrast, is of intermediate pathogenicity for swine with acute clinical signs seen in young pigs and abortions (often in groups) occurring in pregnant swine. Although pomona infections are associated with acute, sometimes severe clinical signs suggestive of an incidental host infection, pigs often remain infected and shed serovar pomona for weeks to a few months after infection. This feature of pomona infection can be associated with high rates of pig-to-pig transmission among swine reared in confinement.

Abortions occurring 2–4 wk before term are the most common manifestation of leptospirosis in pigs. Piglets produced at term may be dead or weak and may die soon after birth. The principal differential diagnosis is porcine reproductive and respiratory syndrome (see Porcine Reproductive and Respiratory Syndrome), although brucellosis, parvovirus, and SMEDI (stillbirth, mummification, embryonic death, and infertility) share some features with leptospirosis. Acute leptospirosis, as described in calves, has been described in piglets but is rare. Treatment and control are similar to those described for cattle using antimicrobials that are indicated for swine.